Waarom is dit emailadres fout ?

The original message was received at Fri, 28 Aug 2015 10:51:28 +0200
from ip-62-235-251-238.dsl.scarlet.be [62.235.251.238]

   ----- The following addresses had permanent fatal errors -----
<maten@trend-friends.be>
    (reason: 550 5.7.1 Blocked by email filter (09572a8f-4d62-11e5-91b7-b82a72d0454d))

   ----- Transcript of session follows -----
... while talking to mxcluster1.one.com.:
>>> DATA
<<< 550 5.7.1 Blocked by email filter (09572a8f-4d62-11e5-91b7-b82a72d0454d)
554 5.0.0 Service unavailable